1. Field of the Invention
The present invention relates to a probe having a giant magnetostrictive material for organism diagnosis which is suitable for an instrument for diagnosing a viscoelasticity characteristic of organism tissue such as hardness of skin and swing of tooth.
2. Related Background Art
A mechanical impedance measurement device for a tooth as shown in FIG. 3 has been known as a diagnosing instrument. It comprises a random signal generator 31 for generating a random wave, a low pass filter 32, a power amplifier 33, a probe 34, a distortion amplifier 36, a charge amplifier 35 and a data processor 37. The probe 34 comprises a vibration excitor 41 which is driven by the output from the random signal generator 31, an impedance head 42 which is driven by the vibration of the vibration excitor 41 to vibrate a periodontium by random vibration and produces an electrical signal proportional to an acceleration of the random vibration and an electrical signal proportional to a vibration stress created in the periodontium vibrates by the random vibration, a tip 42a at an end of the head 42 and a load cell 43 for measuring a contact pressure (hereinafter static load) applied to the periodontium. The data processor 37 processes an electrical signal generated by the impedance head 42 and comprises an A/D converter 51, a personal computer 52 and a printer 53.
In the above mechanical impedance measurement device for tooth, the random wave from the random signal generator 31 is applied to the low pass filter 32, which supplies only components lower than a predetermined frequency (for example, 1 KHz) to the power amplifier 33, which amplifies the input random wave. The amplified random wave vibrates the vibration excitor 41 and the vibration thereof is transmitted to the impedance head 42 through the load cell 43 to vibrate the tip 42a. Because an affect of the static load developed between the periodontium and the tip 42a is large, the static load is measured by the load cell 43 to maintain the static load at a constant level. The static load measured by the load cell 43 is supplied to the strain amplifier 36 and amplified thereby, and the output thereof is sent to display means (not shown) to maintain the static load under measurement at the constant level.
On the other hand, when the tip 42a is contacted to the periodontium to vibrate the periodontium, the impedance head 42 produces a first electrical signal proportional to the acceleration of the input random wave and a second electrical signal proportional to the vibration strain from the vibrated periodontium. Those two electrical signals are amplified by the charge amplifier 35 and they are supplied to the data processor 37. In the data processor 37, they are converted to digital signals by the A/D converter 51 and they are applied to the personal computer and FFT-processed thereby. A transfer function of the system is determined by this process and it is converted to a viscoelasticity, (mechanical impedance) and displayed on a display on real time. It may be printed out by a printer, as may be required. The measurement data may be stored in memory means such as a floppy disk or transferred to other computer (host computer).
The probe of the measurement device uses a combination of an electromagnetic excitor (such as moving magnet or moving coil) or a vibration excitor using a piezo-electric device such as a PZT (PbZrO.sub.3 -PbTiO.sub.3) ceramics, the impedance head and the mechanism for measuring the static load.
It is required to the probe that firstly it is compact, secondly it can be driven with a low voltage and a low current, thirdly it can provide a vibration up to a high frequency, and fourthly it can exactly measure the static load.
However, in the prior art electromagnetic vibration excitor described above, it is difficult to reduce the size while meeting the requirement for the vibration power and amplitude. Further, it can be used only in a low frequency band. Because of low axial rigidity of the vibration excitor, the attitude of the probe is unstable during the measurement and it is difficult to attain exact measurement of the static load. Further, in the vibration excitor which uses the piezo-electric device, the drive voltage and the drive current are large.